Engineering News

Straps Bring Earthquake Battered Buildings Back to Life

Scientists in the UK have developed a simple yet effective technique for remedying the structural weaknesses of buildings damaged by earthquakes.

The technique, developed by scientists from Sheffield University, entails the use of metal straps to fortify the individual floors of earthquake-affected structures. The straps are wrapped around each floor before their tension levels are dialed up either manually or via the use of compressed air tools.

The technique is specifically designed for use with reinforced concrete frame structures, which are among the most common types of buildings on the planet.

Prof. Kypros Pilakoutas

Professor Kypros Pilakoutas, lead researcher for the development of the technology, compared it to the abdominal belts weight-lifters use to increase the ability of their bodies to bear heavy loads.

“The strapping works…by keeping everything tightly compressed to reduce tension on the concrete columns of the structure,” he said. “Concrete works well under compression, but not when pulled under tension and this is why it has to be reinforced for use in construction.”

According to Pilakoutas, the technique possesses a number of virtues, including low cost, ease of use, and speed.

“Our method not only makes the building stable again very quickly, but it increases the building’s ability to deform without breaking, making it more able to withstand further earthquake movement,” he said.

Compared to other repair techniques, the method devised by Pilakoutas’ team does not require specialist technical knowledge or the use of expensive materials, making it particularly advantageous for earthquake-affected areas in the developing world.

For a small residential building with six columns, repair work would cost roughly US$330 and the work could be completed in days. Traditional repair techniques might cost 10 times this amount and require months to complete.

The Sheffield University team has already tested out the technique on full-scale structures. They erected a two-storey building on top of an AZALEE “shaking table” which is capable of simulating the forces produced by strong earthquakes. The structure was built in accordance with outdated European construction standards, leaving it ill-equipped to deal with high-impact seismic events.

Devoid of any structural reinforcement, the building almost collapsed when subjected to a simulated earthquake pegged at around four on the Richter scale.

The damaged building was then repaired and fortified using the post-tensioned metal straps developed by the researchers, which produced remarkable results. The ability of the once-precarious structure to withstand seismic movement was vastly increased, and it was found to be capable of weathering even an earthquake measuring seven on the Richter scale at its epicentre.